http://www.ck12.org Chapter 14. The Properties of Gases
FIGURE 14.1
Nitrogen gas lamp.Physical Characteristics of Gases
All matter, under the right conditions, can exist in a gaseous state. Some substances, such as carbon dioxide, oxygen,
and nitrogen, exist as gases at room temperature under standard atmospheric pressure. Gases have the following
characteristics:
1.Gases assume the volume and shape of their container.When placed in a container of any size and shape,
the gas molecules will quickly distribute themselves evenly throughout the container.
2.Gases are compressible.The volume and pressure of a particular sample of gas can fluctuate greatly simply
by changing the size of its container.
3.Gases mix homogeneously when confined to same container.When several gases are added to a container,
the individual gas particles mix freely, forming a homogeneous mixture in which each type of gas is randomly
distributed throughout all the available volume.
4.Gases have much lower densities than liquids and solids. For example, liquid water is over 1000 times
more dense than water vapor at STP.The following simulation demonstrates the properties of gases listed above: http://phet.colorado.edu/en/simulation/s
tates-of-matter.
Pressure
According to the kinetic-molecular theory, momentum is conserved in collisions between particles at the molecular
level. The same can be assumed to be true for collisions between gaseous particles and the wall of their container